Parkinson's Disease and a Plant Based Diet

Kathrynne Holden, MS, RD
Summer 2000

The nature of Parkinsonís disease

Parkinsonís disease (PD) afflicts about one to one and one-half
million people in the United States (Tanner 1992). PD is a progressive
neurological disorder that results in the death of dopamine-producing
cells in the brain. Loss of dopamine affects movement, both of skeletal
muscle and the smooth muscle of the gastrointestinal (GI) tract. This
can result in slow, shuffling gait, resting tremor, and/or slowed
peristalsis. Individuals with PD may experience frequent falls (Dolinis
et al., 1997; Northrid ge et al., 1996), d ifficulty handling cooking
and eating utensils, and such GI-related problems as slow stomach
emptying, gastroesophageal reflux, and chronic constipation (Jost WH,
1997; Edwards et al, 1993; Edwards et al., 1994; Byrne et al., 1994).

There are also indications that B vitamin deficiencies may be of
concern, although the causes are not clearly understood. In 1979, Bender
et al. reported the possibility that users of levodopa-carbidopa (Sinemet,
Sinemet CR, a medication used to treat the symptoms of PD) could be at
risk for both niacin and vitamin B6 deficiencies. Long-time users of
levodopa-carbidopa have since been found to have increased levels of
serum homocysteine (Kuhn et al., 1998, Muller et al., 1999), implicating
vitamins B6, folate, and B12. In attempts to determine the etiology of
PD, Hellenbrand et al. compared the dietary habits of patients vs. a
control group; patients were found to have consumed significantly less
niacin than controls (Hellenbrand et al. 1996). In a more recent Swedish
study researchers note that consumption of niacin-containing foods
appeared to reduce risk for PD (Fall et al., 1999). Finally, in an
unpublished study, pellagra was discovered in several patients using
levodopa-carbidopa (Iacono et al.). Thus, patients could have increased
risk for vascular disease, pellagra, and other conditions resulting from
deficiencies of B vitamins.

Constipation is very common due to the disease and/or to the
medications used to treat PD (Jost, 1997; Jost and Schrank, 1998;
McIntosh and Holden, 1999). Chronic constipation can raise the risk for
fecal impaction (Sonnenberg et al., 1994) and colon cancer (Jacobs and
White, 1998; Will et al., 1998), therefore, safe methods of controlling
constipation are desirable.

Furthermore, PD brings with it a food-medication interaction that has
been generally under-addressed by dietetics professionals. Levodopa, the
primary medication used to treat PD, competes with the five large
neutral amino acids for carriers, both in the gut and at the blood-brain
barrier (Lieberman, 1992). Thus, levodopa absorption is effectively
blocked if taken with meals.

How can a vegetarian or plant-based diet be of help to people with
PD?

While research has failed to conclusively show a link between diet
and PD, nevertheless, fiber, nutrients found particularly in plants, and
protein, are excellent reasons to choose among the various vegetarian
and plant-based eating plans. Animal foods are often high in protein and
lack fiber. Plants in general have a high proportion of carbohydrate,
with moderate amounts of protein. Plants also contain fiber and many
phytochemicals, which animal products do not.

Fiber. A plant-based diet is generally richer in fiber, which
can alleviate constipation, and thereby reduce risk for fecal impaction
and colorectal cancer. In a pilot study, McIntosh and Holden found that
while 21 out of 24 patients reported frequent constipation, analysis of
three-day food diaries showed that 18 patients reported intake of fewer
than 25 grams of dietary fiber daily. Education in the need for greater
fiber intake, and its benefits to health, is necessary for PD patients.
Additionally, a high-fiber eating plan may promote bioavailability of
levodopa. Astarloa et al. found a correlation between a diet rich in
insoluble fiber and plasma levodopa concentration, and postulate that
the improvement of constipation may have a positive effect upon levodopa
availability (Astarloa et al., 1992). While there is no research as yet
on benefits of a vegetarian diet for people with PD, nevertheless, a
vegetarian or plant-based diet may have special significance for people
with PD.

Unplanned weight loss. To combat weight loss, patients must
consume more calories. Yet delayed stomach emptying, if present, may
require moderate use of fatty foods, while those using levodopa may need
to control their use of protein. Such restrictions sometimes necessitate
small, frequent meals and snacks, and a diet high in carbohydrates. A
vegetarian diet adapts very well to such an eating plan, as it can be
both high in carbohydrates and low in fat, whereas animal foods are
often high in fat.

Chewing/swallowing difficulty. Patients in mid-to-late stages
of PD may experience difficulty chewing food, and/or moving the tongue
to position food properly for swallowing. The normal esophageal
peristalsis may be slowed, resulting in choking. While a swallowing
evaluation should be performed, along with education in safe swallowing
techniques, it should be noted that plant foods may be easier to chew
than many meats; plant foods also can be chopped, mashed, or pureed
easily to provide the best consistency for the individualís needs while
retaining valuable fibers and phytochemicals.

Nutrients. Plant foods are rich in magnesium and vitamin K,
important to bone health. This should be emphasized, as PD patients, due
to the nature of the disease, may be prone to falls (Ishizaki et al.,
1993; Kao et al., 1994; Taggart, et al., 1995; Revilla et al., 1996;
Koller et al., 1989; Johnell et al., 1992, Sato et al., 1997), and
therefore more susceptible to fractures (Dolinis et al., 1997;
Northridge et al., 1996). Good sources of calcium and vitamin D must be
highlighted, also, as there may be a greater need for these in this
population; in a controlled study, Sato et al. found increased incidence
of vitamin D deficiency and reduced bone mass in individuals with PD
(Sato et al., 1997).

A vegetarian or plant-based diet can provide excellent amounts of the
B vitamins (with the possible exception of B12), especially folate; and
education regarding need for B vitamins is important. The vegan patient
may need to use a supplement of vitamin B12, and in fact, if
deficiencies are suspected, a B complex may be required, at least
temporarily. It should be noted that large amounts of vitamin B6 (over
ten mg per day) may reverse the effects of levodopa; therefore,
supplements should be taken with meals, with levodopa taken at least 30
minutes prior to meals, to avoid this food-medication interaction.

Protein-levodopa interactions. As stated before, protein
breaks down in the gut to individual amino acids, with which levodopa
must compete for carriers across the intestinal wall. For this reason,
patients must take levodopa at least 30 minutes prior to meals or
snacks. As the disease progresses, individuals often begin to experience
fluctuations in their response to levodopa, resulting in the "on-off"
phenomenon, a condition wherein a dose of levodopa wears off before the
next dose is due. Without levodopa, the individual may be able to move
only very slowly, or not at all, and is effectively disabled.

To cope with these motor fluctuations, it has long been advised that
patients avoid protein during the day, limiting intake to no more than
ten grams prior to the evening meal. The bulk of protein needs is met at
the evening meal, allowing the patient optimal use of levodopa during
the daytime hours. However, this often means that the patient cannot
move all night long, which can be very frustrating and even frightening,
as s/he cannot turn over in bed, get up to use the bathroom, or adjust
the bedclothes. If diabetes, hypoglycemia or other conditions are
present, this protein restriction is even less desirable.

Although less widely understood, a high-carbohydrate eating plan
consisting of a ratio of five parts carbohydrate to one part protein, or
higher, can be very effective (Berry 1991). Once in the bloodstream, the
high ratio of carbohydrates causes an insulin rush that removes amino
acids from the blood as well, thus allowing levodopa to reach the
blood-brain barrier unobstructed. (See Eriksson et al. 1988; Sanchis et
al. 1991.) A plant-based diet is an ideal way to achieve a
high-carbohydrate meal plan, as plant proteins are often found in a
carbohydrate-to-protein ratio of 3:1 or higher, whereas meats have
virtually no carbohydrate. Legumes, seeds, and nuts are excellent foods,
and can easily be incorporated into a meal consisting of a 5:1 or higher
ratio.

Most patients gain improved "on time" with some form of protein
adjustment. Some find they can reduce the amount of levodopa needed.
Reduction of levodopa may result in lessened side effects, such as
hallucinations and dyskinesia (unwanted twisting or writhing movements).
Much more research is needed in this area, to document reduction in
medications, improved "on time, lessened dyskinesia, and reduced adverse
effects of medications.

Counseling/therapy

It will be important to assess nutrition risk, and a three-day
food diary can be of great help in determining whether fiber and
nutrient intake is adequate. Information intake via interview is
also important, paying particular attention to weight changes and risk
for bone thinning. If unplanned weight loss has occurred, determine
whether this is due to depression, excessive calorie expenditure because
of tremor, dyskinesias, or rigidity, inability to self-feed at a normal
pace, chewing or swallowing problems, or other condition. Small,
frequent meals and snacks are often preferable to the usual three meals
a day. To assess delayed stomach emptying, inquire whether the
individual experiences heartburn or acid reflux, often a sign of slowed
peristalsis; also find out how long it takes for medications to take
effect. If the patient is using levodopa, and taking it at least 30
minutes prior to meals without feeling the onset of antiparkinson
effects, delayed stomach emptying is a possible factor. Small
plant-based meals and snacks, moderate in fat, may be an effective way
to counter delayed stomach emptying.

If the individual uses levodopa and motor fluctuations occur,
consider protein adjustment. The simplest, and often very effective
method, is to estimate individual protein needs, and divide the protein
equally among meals. If weight loss or slowed stomach emptying is
present, I often suggest small meals with low-protein snacks between
meals. This provides the most natural eating plan. If the person is
protein-sensitive, it may be helpful to increase carbohydrates. Try a
ratio of 5:1 initially, as this provides the most protein and therefore
a more natural eating plan. After two to three weeks, the individual
should notice improved "on time;" if not, increase the ratio to 6:1 or
7:1. This eating plan is often harder to teach; it may be necessary to
provide ready-made menus for meals and snacks. NOTE: it is difficult to
provide a 7:1 eating plan having less than 1800 kcal per day. This may
be too much food for some people, especially small women. If a 7:1 ratio
works well for the person, s/he may wish to use it throughout the day in
small meals and snacks, then add additional protein at the evening meal.
This will provide for a smaller number of calories and offer sufficient
protein, while still allowing for better levodopa absorption during the
day.

Some cautions to be aware of are the increased risk for bone
thinning, and need for vitamin B12. It may be necessary for patients to
use vitamin/mineral supplements, especially of calcium, vitamin D, and
vitamin B12. In some cases, a vitamin B complex may be needed as well.
Patients who use levodopa should take supplements containing large
amounts of vitamin B6 with meals, at least 30 minutes after taking
levodopa, in order to avoid the interference of vitamin B6 with levodopa
absorption.

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